Membrane peptidase expression by confluent cultures of Caco-2 cells

Contluent cultures of Caco-2 cells, a human colonic carcinoma cell line, undergo differentiation into enterocyte-like cells and are widely used as a model system to study the expression of membrane peptidases on the apical brush border [I-41 Indirect irnniunofluorescent staining has previously shown dipeptidylpeptidase IV (DPPIV, EC 3 4 14 5) to be homogeneously distributed on the surface of Caco-2 cells [ I ] whereas endopeptidase-24 1 1 (E-24 I I , EC 3 4 24 I I ) was found on the surface of some cells but not on others [4] This observation has also been reported by Jalal e/ d. [ S ] who have shown that E-24 1 1 is expressed by all cells but in some is confined to an intracellular pool In the present study the cellsurface and intracellular expression of five membrane peptidases on confluent cultures of Caco-2 cells has been investigated using indirect immunofluorescent staining The membrane peptidases studied were DPPIV, E-24 I I , angiotensin converting enzyme (ACE, EC 3 4 15 I). aminopeptidase N (AP-N, EC 3 4 1 I 2) and aminopeptidase W (AP-W, EC 3 4 11 16)